Catalytic dehydrogenation



Patented June 26, 1945 Walter F. Huppke, Lomita,

and Theodore Vermeulen, Los Angeles, Calif.,' assignors to Union Oil Company of California, Los Angeles, Calif., a corporation of California 1% Drawing. Application January 15, 1940, Serial No. 313,935

Claims.

This invention relates to catalysts and cat-- alytic'processes for the dehydrogenation of various hydrocarbons. More particularly,- the invention relates to the production of .unsaturates from the light or normally gaseous hydrocarbons such as ropane, butane, isobutane and the like.

The principal objects of the invention are to provide an efficient catalyst which is compara tively easy to produce, is longlived, is not easily poisoned and at the same time causes anadeactivated by the presence of a small proportion,

for example about 2%, of an activating oxide which is soluble in the molten boric oxide. Such an activating oxide is zinc oxide, but other oxides such as uranium oxide, which are soluble inthe molten boric oxide may be used. The invention also resides in the method of producing unsaturates from the saturated light hydrocarbons, par.- ticularly the normally gaseous petroleum hydrocarbons such as propane and butane, by passing the hydrocarbon gases or' vapors through a molten body of the catalyst. The invention also resides in the dehydrogenation or similar conversion of hydrocarbons by contact with boric oxide activated with a small percentage of an activating oxide such as zinc oxide, without respect as to whether the catalyst is molten or solid.

According to one form of practicing the present invention a molten boric oxide bath is prepared in an iron. vessel or other appropriate vessel, and into this bath there is introduced an activatin proportion of an activating oxide which preferably is soluble in the molten boric oxide. In gen.- eral about 2% of such an activating oxide is employed, but this may be varied within appropriate ranges such as between about 1% and about 5%. Other activatingoxides which can be employed. and most of which are adequately soluble in molten boric oxide are the oxides or iron, copper, vanadium and uranium. Apparently any oxide soluble in the molten boric oxide is effective, and some oxides such as uranium oxide which are not soluble in the molten boric oxide nevertheless possess activating properties when well dispersed through the melt. The molten boric oxide melts at about 1065 F. and is quite viscous up to a temperature of about 1100 F. Preferred operating ranges are from a little under 1200 F. to about 1250 F. Even at these ranges the viscosity of the melt is sufficient to maintain suspension of an insoluble activator during the operating conditions. The various usable oxides are stable oxides, that is, in order to be present as oxides in the catalytic mass during treatment their form will not change under the operating conditions.

The molten boric oxide containing the activating oxide as above indicated is placed in a vertical elongated iron reactor vessel or the like through. hich the gaseous or vaporoushydrocarbon to be treated may be bubbled. For ex ample, a vertical cylinder about six inches in diameter and three or four-feet high whose walls are provided with suitable heating means such as electric heating elements'andwhich contains inits lower end means for distributing andfbubbling the gases or'vapors uniformlythrou'gh the melt, constitutes satisfactory equipment. The heating means must be adapted to raisethe'temperature to the required range of about 1200" F. to about 1250'FI The line through which the gaseous or vaporous hydrocarbons are introduced should contain a preheater to raise thematerials to be treated to a temperature approximating that of the reactor vessel. v

The treatment consists simply in'introducing preheated vaporous or gaseous hydrocarbons into the bottom of the reactor vessel through the distributor means mentioned so that such materials will bubble upward through the molten boric oxide mass. Therate of feedat the height of the molten mass should be such that the contact time of the vaporous material with the molten mass approximates one second, a contact-range between about 0.1 second and 5.0 seconds appearing to be permissible. U

Where operating with a ten inch. column of molten boric oxide containing2% ,Qfrzinc oxide dissolved therein, and bubblin propane gas up through the column mass at 1200 F. approxi mately 20% of the feed was converted into unsaturates, a typical analysis of the product being Where operating at the lower temperatures of 1150 F. the conversion rate was about 5%; at 1200" F. the conversion rate was about 10% and at 1250 F. the conversion to unsaturates was about 24%, but the formation of tar and excessive amounts of methane commenced. In other instances a conversion rate of about 24% at 1250 F. was obtained without appreciable carbon or tar formation. In other instances where about /2% of uranium oxide was added to the boric oxide melt containing zinc oxide a conversion rate of about 23% wasiobtained :at 120U F. At temperatures around 1300 F. cracking with theformation of tars, carbon and methane predominates.

While we have found molten boric oxide containing a small percentage of activating exide as ha been described, to be most effective for the conversion of hydrocarbons, we have also found that a similar material may be *p'reparedin solid form by depositing the boric-oxideandactivating oxide on a carrier such as alundum granules. This can be done, for example, by dissolving :20 parts of boric oxide and 4 parts of zinc nitrate in a minimum of boiling water and adding this to 100 parts of alundum granules, and then heating slowly untilall the water =is=driven ofirand the mitrate is decomposed to leave .the oxide. Thismaterial has been used in :beds in silica tubes, :and isobutane passed thereover .at -a .contact .rate :of about 0.8 seconds per pass at temperatures of about 1=150 F. to .1200" with a conversion rate into 'unsaturates of about 22%.. With propane the conversion .rate is somewhat lower.

The value of the .boric oxide and the activating zinc oxide is .shown .by-eomparing a test of :the alundum ggranules alone under the-same -conditions where aconversionof mini-5 5% was ob- ;tained which may be :classed as .wholly .pyrolytic conversion. Here, again the activating .oxide may be any of the type .above'described. .-In em- ."7

ploying .catalystson-a carrier. of this type-the deed material should be preheated as where .using the molten form, and temperature ranges for the various types of :materials treated will be em- ,ployed approximately .as when using the vmolten .form of catalyst.

In employing this solid .form .of catalyst, other refractory carriers than alundum may be em- -.ployed such as silica gels, and gels precipitated with ammonium hydroxide or the like .such .as zirconium, thorium, .and aluminum gels which are in .fact hydrous ,gels which have not been treated to the .point-of complete dehydration .and

still possess their characteristic porous gel structure and iadsorptive properties.

It is tobe understood that .these disclosures-are illustrative of the generic inventionandare .not

to be taken as limiting except as restrictedby the appended claims.

We claim:

.l. A method for the conversion .of .h-ydrocarbons to change .their .carbon-tohydrogen ratio comprising subjecting saturated hydrocarbons in gaseous state at temperatures between (about 1100 Band 1300" .F. to the influence of.molten boric oxide containing a small proportion of ,an activating metallic oxide.

2. A'method for the'conversion of saturated hydrocarbons comprising subjecting the saturated hydrocarbons to the action of molten boric oxide containing an activating proportion of zinc oxide at conversion temperatures.

3. A method for dehydrogenating hydrocarbons comprising ipassing gaseous or vaporous hydrocarbons-through molten boric oxide at a temperature between about 1100 F. and about 1300 F. and containing between about 1% and about 5% -of.zinc oxide.

4. A method for the conversion of hydrocarbons :to -.change their carbon-to-hydrogen ratio comprising massing saturated normally gaseous hydrocarbons in agaseous state through molten boric oxide containing an activating proportion of..a stable metaloxide at temperatures between 11110051. and 1300 F.

5. A method for the dehydrogenation of saturated hydrocarbons comprising passing a preheated hydrocarbon in gaseous or vaporous state through .a molten mass of boric .oxide containing an activating proportion of en activating stable .metallic oxide .at elevated temperatures .in the order .of 110.0" 1to 13fl0 .F. :to effect unsaturation .ofsaturated materials.

6. Amethod according 'to claim 1 wherein the saturated hydrocarbon ;is alight hydrocarbon.

'7. A method according to c1aim 2 wherein the saturated hydrocarbon is a normally gaseoushydrocarbon.

8. Amethod 'accordingto claim '3 wherein the hydrocarbon treated is a normally gaseous hydrocarbon.

9. 'Ame'thod according'to claim 5 wherein the hydrocarbon treated "is a normally gaseous -hydrocarbon. p

.10. A-method according to claim 5 wherein-the preheated-gases or-vaporsare bubbled-up through the molten mass at a rate to yield a contact period of about 0:1secondto five seconds.

11. A method according to-claim-5 wherein the activating oxide is soluble in the molten 'boric oxide.

12. Amethod for cracking hydrocarbonscomprising passing gaseous or vaporous hydrocarbons at conversion temperature through amolten mass' o'f boric oxide containing a small proportion of a stable activating metallic oxide.

13. Amethod according to 'claim 1 wherein the activating oxide-is selected from theclass consisting of zinc oxide, iron oxide, copper oxide, vanadium'oxide and uranium oxide.

14. 'Armethodaccordirrg'to claim '4 wherein the activating metal oxide is -zinc oxide.

'15. A'method according'to claim 5 wherein the hydrocarbon treated -iis propane and the activating-:oxide is=from the classconsisting of zinc, iron, copper, vanadium and uranium oxides. 

